Low noise level internal combustion engine

Abstract: The present invention provides a low noise level internal combustion engine including a cylinder block (2) without a skirt portion, a supporting member (10) for supporting a journal portion of the crankshaft (9), the supporting member being fixed to a lower end portion of the cylinder block, a shroud (30) for suppressing an explosion sound in a cylinder and a bearing sound to be radiated out of the engine, the shroud being integrally formed with a cylinder head fixed to an upper side of the cylinder block whereby the shroud is spaced from the cylinder block. A noise insulating member (28) is disposed between the shroud and an oil pan (38) for increasing a flexural rigidity of the shroud and oil pan, whereby the present invention provides a low noise level internal combustion engine which can increase a flexural rigidity of a skirt portion without increasing a wall thickness of the cylinder block or using a high strength material, and provides a low noise level internal combustion engine in which a bearing cap supporting a journal portion of a crankshaft are separated from each other and assembled by a coupling member.

Description: The present invention relates to a low noise level internal combustion engine and, more particularly, to an internal combustion engine having a multi-cylinder which can suppress engine noise transmitted to a cylinder block from a journal portion of a crankshaft at a considerably low level. Generally, in conventional reciprocating piston engines, a journal portion of a crankshaft is rotatably supported by main bearings whose upper-half parts are carried by a cylinder block. The lower-half parts of the main bearings are carried by bearing caps. The cylinder block is integrally provided at its bottom portion with a skirt portion. The skirt portion is bulged out to cover the rotating crankshaft with a space between the crankshaft and the skirt portion. An oil pan for reserving an engine oil is fixed to the skirt portion. With the recent trend of higher rotation and higher output of the engine, many methods for reducing noises and vibrations of the engine have been proposed. Since most vibrations and noises of the engine are propagated to other portions through the cylinder block portion of the engine and the bearing portions of the crankshaft, it is most important to enhance the rigidity of these parts in order to reduce the vibrations and noises. From this point of view, a wall thickness of the cylinder block portion is increased in thickness, or formed of a high strength material to reduce the vibrations and noises. However, this proposal gives rise to another inconvenience such that the weight of the engine itself is increased. Schemes for reducing noises and vibrations are proposed in U.S. Patent Nos. 4,213,440, 4,230,087, and 4,412,516. GB-A-200 8195 discloses an engine according to the preamble of claim 1. However, all of the schemes provide only the sound-insulating member and do not provide means which can increase a flexural rigidity of the skirt portion. Accordingly, the present invention has been made in an effort to solve the above-described problems. It is an object of the present invention to provide a low noise level internal combustion engine which can increase a flexural rigidity of a skirt portion without increasing a wall thickness of a cylinder block or using a high strength material. It is another object of the present invention to provide a low noise level internal combustion engine in which a bearing cap supporting a journal portion of a crankshaft are separated from each other and assembled by a coupling means. To achieve the above objects, the present invention provides a low noise level internal combustion engine comprising: a cylinder block without a skirt portion; supporting means for supporting a journal portion of the crankshaft, said supporting means being fixed to a lower end portion of said cylinder block, a shroud for suppressing an explosion sound in a cylinder and a bearing sound to be radiated out of the engine, the shroud being preferably integrally formed with a cylinder head fixed to an upper side of said cylinder block whereby the shroud is spaced from the cylinder block; and noise insulating means, disposed between said shroud and an oil pan, for increasing a flexural rigidity of said shroud and oil pan. Further objects and other advantages of the invention will become apparent from the following description in which the invention is described by way of example only with reference to the attached drawings, in which: Figure 1 is a sectional view taken in a vertical direction with respect to a longitudinal direction of a crankshaft of a low noise level combustion engine according to a preferred embodiment of the present invention; Figure 2 is an exploded perspective view of a bearing cap of the low noise level combustion engine according to a preferred embodiment of the present invention; Figure 3 is a sectional view taken in a longitudinal direction of a crankshaft of the low noise level combustion engine according to a preferred embodiment of the present invention; Figure 4 is a plan view of a vibration absorption member of the low level combustion engine according to a preferred embodiment of the present invention; Figure 5 is a sectional view taken along lines 5-5 of Figure 4; Figure 6 is a sectional view taken along lines 6-6 of Figure 5; Figure 7 is a sectional view taken along lines 7-7 of Figure 5; and FIG. 8 is a sectional view taken along lines 8-8 of FIG. 5. Referring to FIG. 1, a cylinder block 2 generally forms a water jacket 4 for circulating a cooling water. A bore 6 has open upper and lower portions. The cylinder block 2 does not have a skirt portion or a bearing cap for supporting a journal of a crankshaft which are generally formed on a conventional cylinder block. As described above, the present invention provides the cylinder block 2 without the skirt portion or the bearing cap, and thus, the present invention provides a special supporting member 10 which serves as the skirt portion and the bearing cap, as shown in FIG. 2. The supporting member is provided with an upper bearing cap 12 and a lower bearing cap 14. The upper and lower bearing caps have respectively bearing support portions 16, 18 having a semi-circular configuration. A journal portion 9 of a crankshaft 8 is supported between the bearing support portions 16, 18. A plurality of rectangular holes 20 are formed at the upper half bearing cap 12 so as to provide a rotating space of a balance weight B when the crankshaft 8 rotates. Further, elongated holes 24 are provided on the upper and lower half bearing caps 12, 14 to assemble them with each other by bolts 22. A sound-insulating member is disposed under the supporting member 10. The sound-insulating member is fixed on a shroud 30 which is integrally formed with a cylinder head 26 by bolts for suppressing a vibration of the shroud 30. The shroud 30 includes an upper portion 32 slightly spaced from the cylinder block and a lower portion 34 extending widely from the upper portion. The shroud 30 is provided at its outer side with a plurality of ribs 35 to increase a structural rigidity thereof. A boss 36 is formed on the lower end of the lower portion 34 of the shroud 30. The sound-insulating member and an oil pan 38 are fixed to the boss 36 and provided with a gasket therebetween. Referring to FIG. 3, a bearing 40 is located at both sides of the cylinder 2 to smoothly rotate the crankshaft penetrating the cylinder block 2. Cases 44, 46 having a seal 42, respectively, are also mounted on both sides of the cylinder block 2, respectively, to prevent an oil leakage caused by the crankshaft 8 penetrating the cylinder block 2. The cases 44, 46 are mounted on the cylinder block 2 by bolts and fixed at their lower end to the oil pan 38. The sound-insulating member 28 is provided with a plate 48 and a plurality of ribs 70, 72, 74, 76, 78, and 80 integrally formed with the plate 48, as shown in FIGS. 4 through 8. The plate 48 is provided with slits 50, 52 to exhaust oil dropped from a crank mechanism into the oil pan 38. Both side ends of each slit 50, 52 are located between bends 54, 56 and 54', 56', respectively, which are bent from a surface of the plate downward, such that the oil from the crank mechanism is directly transmitted to the oil pan, whereby the oil can be used for lubrication. Each slit is provided at its left and right sides with grooves 58, 60, 62, 64, 66, and 68 in a right direction with respect to a longitudinal direction of the crankshaft 8 to be lower than a surface 49 of the plate 48. The grooves 58, 60, 62, 64, 66, and 68 are integrally formed with the ribs 70, 72, 74, 76, 78, and 80, respectively, thereby increasing in flexural rigidity. Further, as shown in FIG. 6, the plate 48 is slightly bent to effectively absorb a vibration of the shroud 30. FIG. 8 is a sectional view of the grooves 58 through 68, wherein a central portion of each groove is bent downward and ribs 82, 84, and 86 are integrally formed with a bottom of each groove. In the low noise level internal combustion engine as described above, when the crankshaft rotates by engine driving, vibration generated at the journal portion of the crankshaft 8 is transmitted to the supporting member 10 and then separately transmitted to the upper bearing cap 12 and the lower bearing cap 14. The vibration transmitted to the upper bearing cap 12 is transmitted to the cylinder block 2. At this point, since the cylinder block is fixed to the supporting member 10 by the bolts 22, the vibration is indirectly transmitted to the cylinder block 2, thereby reducing the vibration. Further, since the crankshaft 8 and the supporting member 10 are spaced away from the shroud 30 and the shroud 30 is integrally formed with the cylinder head 26, the vibration from the journal portion of the crankshaft 8 is reduced to a considerably low level. Although the low level vibration acts on the lower portion of the shroud 30, since the lower portion of the shroud 30 is fixed to the noise-insulation member 28 for increasing the flexural rigidity of the shroud 30, the vibration is suppressed. Also, since the oil pan 38 is fixed to the noise-insulation member 28, the vibration of the oil pan is suppressed. In addition, the shroud 30 prevents the explosion sound in a cylinder from being radiated out of the engine through the cylinder block, and the plate 48 prevents the explosion sound in the cylinder and the bearing sound from being transmitted to the oil pan, thereby realizing the low noise internal combustion engine.

Claims: A low noise level combustion engine comprising: a cylinder block (2) without a skirt portion; supporting means (10) for supporting a journal position of the crankshaft, said supporting means being fixed to a lower end portion of said cylinder block; a shroud (30) for suppressing an explosion sound in a cylinder and bearing sound to be radiated out of the engine, the shroud depending from a cylinder head (26) fixed to an upper side of said cylinder block whereby the shroud is spaced from the cylinder block; and characterised by noise insulating means (28), disposed between said shroud and an oil pan (38), for increasing a flexural rigidity of said shroud and oil pan and decreasing noise. A combustion engine as claimed in claim 1, wherein the shroud comprises an upper portion (32) disposed in parallel with said cylinder block, a lower portion (34) widely extending from said upper portion, and at least one rib (35) integrally formed with the upper and lower portions to increase the rigidity of the upper and lower portions. A combustion engine as claimed in claim 1 or 2, wherein said supporting means includes an upper bearing cap (12) having a plurality of rectangular holes (20) formed therethrough for providing a rotating space of balance weights of the crankshaft and a respective lower bearing cap (14) connected with the upper bearing cap by a bolt. A combustion engine as claimed in claim 1, 2 or 3, wherein said noise-insulating means is formed by a plate (48) which is bent in a right direction with respect to a longitudinal direction of the crankshaft. A combustion engine as claimed in claim 4, wherein said plate comprises at least one slit (50, 52) for transmitting oil from a crank mechanism to the oil pan, and a plurality of grooves (60, 62; 64, 66) formed on both sides of the slit to be lower than a surface of the plate for increasing structural rigidity. A combustion engine as claimed in any one of the preceding claims, in which the cylinder block is provided with at least one case (44, 46) having a seal 42. A combustion engine as claimed in claim 4, wherein said plate includes a plurality of ribs (70, 72, 74, 76, 78, 80) integrally formed therewith for increasing structural rigidity. A combustion engine as claimed in any one of the preceding claims in which the shroud (30) is integrally formed with the cylinder head (26).

Inventors: HAN JEIWON, HAN, JEIWON
Applicants: HYUNDAI MOTOR CO LTD, HYUNDAI MOTOR COMPANY
Application year: 1994
Main classification: F02F7
IPC codes: F02F7, F02F1, F01M11